It is proposed in this study to determine the mechanisms of action and the chemical characteristics of a possibly-steroid pheromone produced by the female cells of a freshwater green alga, Oedogonium. This pheromone controls two aspects of the sexual reproductive process: morphogenesis and de novo synthesis of pheromone by the male. Both of these aspects have potential to serve as tools in uncovering methods of gene regulation in higher organisms. Through the co-operative efforts of a physiologist (Principle investigator), a bio-organic chemist (Co-investigator), and their students, two parallel paths are proposed in this study. The physiologist and students will investigate the means by which the pheromone effects morphogenetic control and will attempt to isolate the male-produced pheromone for further study. The techniques of gel electrophoresis, to determine whether unique proteins are synthesized by the androspores during pheromone-induced morphogenesis, and of in vivo transcription and translation inhibitors, to determine the level at which control is operative, will be employed in this part of the study. The bio-organic chemist and students will attempt to determine the chemical characteristics of the pheromone employing Nuclear Magnetic Resonance (NMR) and mass spectrometry. There is circumstantial evidence, based upon preliminary isolation and purification studies and by analogy to other examples of morphogenetic control, that this interactive system employs steroid or steroid-like pheromones for some or all of the physiological responses invoked. If proven to be the case, the implications are far-reaching in the studies of steriod hormone control of morphogenesis in all types of cellular developmental problems, for the cells are haploid and easily proliferated as genetic clones in all phases of their growth. On the other hand, should the system prove to employ compounds other than steroids for morphogenetic control, it opens the possibilities for investigation of new classes of compounds operative in gene regulation, which could have substantial implications for expanding our understanding of such systems.